The objectives of this research are to investigate the translation and regulation of macromolecules of neural interest. Attempts are being made to localize and translate the messenger RNA for the enzyme tyrosine hydroxylase. If such a message can be measured, it will be used as a tool for the study of the induction of the enzyme by nerve growth factor, and for a number of experiments on other influences which impinge on the enzyme. Other experiments are pointed at the isolation of the message for the nerve growth factor itself. Another line of investigation involves a search for the mechanism of the biosynthesis of the proteolipid proteins which are found in the myelin. Earlier data from other laboratories indicated that these proteins were made in the mitochondria. It has been shown recently that mitochondria do, indeed, make proteins which have the general characteristics of the proteolipids, and that the mitochondria from young brain make much more than do comparable mitochondria from the brains of adults or from the livers of newborn animals. If it can be shown that the synthesized material is indeed the proteolipid of the myelin, then an attempt will be made to isolate, translate, and characterize the messenger RNA.